button { 
    cursor: pointer;
    display: inline-block;
    height: 2rem;
    padding: 0 1rem;
    outline: none;
    vertical-align: middle;
    color: #fff;
    background-color: #0091ea;
    text-align: center;
    border-radius: 0.125rem;
    -webkit-transition: all .25s ease-in-out;
    transition: all .25s ease-in-out;
    border: 1px solid #0091ea;
    font-size: 14px;
    white-space: nowrap;
    margin-right: 20px;
    margin-bottom: 10px;
}
button:hover { 
    border-color: #36acef;
    background-color: #36acef;
}

.tip {
    font-size: 16px;
    color: #666;
    margin-bottom: 20px;
}
.top {
    display: flex;
}

.center {
    margin-top: 10px;
}